1. Field of the Invention
This invention relates to a material testing machine for testing specimens by applying thereto tensile forces in biaxial directions perpendicular to each other.
2. Description of the Prior Art
Such material test is also called a biaxial tensile test, which is conducted when measuring the strength of a metal plate, for example. Japanese Unexamined Patent Publication No. 2012-32218 discloses, as such a material testing machine, a biaxial tensile testing machine which includes a pair of specimen chucks movably arranged on each of two rails extending in directions perpendicular to each other.
FIG. 11 is a perspective view showing a biaxial tension mechanism for applying testing forces to a specimen 100 in such conventional material testing machine.
The biaxial tension mechanism in this material testing machine includes a first rail 91 and a second rail 92 arranged on the surface of a base plate 90 to extend in directions perpendicular to each other. The first rail 91 has a pair of first moving members 93 slidably arranged thereon. These first moving members 93, by being guided by the first rail 91, are movable toward and away from each other along the first rail 91. Each of these first moving members 93 has a chuck 95 for gripping the specimen 100. On the other hand, the second rail 92 has a pair of second moving members 94 (only one of them appearing in FIG. 11) slidably arranged thereon. These second moving members 94, by being guided by the second rail 92, are movable toward and away from each other along the second rail 92. Each of these second moving members 94 has a chuck 96 for gripping the specimen 100. The base plate 90 which supports the first rail 91 and second rail 92 is disposed on a base block in a material testing machine body.
This biaxial tension mechanism includes a load member 80 connected to a crosshead in the material testing machine, for receiving a load applied from the crosshead. The pair of first moving members 93 are connected to the load member 80 by link members 83 each formed of a link 81 and a link 82. The link 81 forming part of each link member 83 is rockably connected to the first moving member 93 by a pivot 97. The link 82 forming part of each link member 83 is rockably connected to the load member 80 by a pivot 85. The pair of second moving members 94 are connected to the load member 80 by link members 84. One end of each link member 84 is rockably connected to the second moving member 94 by a pivot 98. The other end of each link member 84 is rockably connected to the load member 80 by a pivot 86.
With the biaxial tension mechanism in this material testing machine, when the load member 80 is pressed in a state of the specimen 100 gripped by the two pairs of chucks 95 and 96, the pair of first moving members 93 are moved, by action of the link members 83, away from each other along the first rail 91, and the pair of second moving members 94 are moved, by action of the link members 84, away from each other along the second rail 92. Consequently, tension loads in the biaxial directions perpendicular to each other are applied to the specimen 100 gripped by the two pairs of chucks 95 and 96.
As noted above, the biaxial tension mechanism of the material testing machine described in Japanese Unexamined Patent Publication No. 2012-32218 has a construction in which the pair of first moving members 93 and the load member 80 are connected by the link members 83, and the pair of second moving members 94 and the load member 80 are connected by the link members 84. With this construction, when placing the specimen 100 in a state gripped by the chucks 95 and 96 or detaching the specimen 100, the operator needs to put in their hands through gaps between the link members 83 and 84 to carry out an attaching or detaching operation, which constitutes bad working efficiency. Particularly when a tool such as a spanner needs to be used in attaching or detaching the specimen 100 to/from the chucks 95 and 96, there arises a problem of requiring a very long time for attaching or detaching the specimen 100, which is due to interference between the tool and the link members 83 and 84.